Browser Computer-32 Specification

Notes

This is missing a lot of stuff like functions and labels, it's a WIP.
The interface is both hideous (I prefer the term "functional") and unwieldy on mobile, I'll work on styling it once I finish the core functionality.
There are quite a few differences between this and “real” x86, namely an incrementing stack and more liberal use of immediates, these are intentional so as to help people grasp the basics of assembly programming.
If anyone wants to help me work on it (especially frontend), or just has some thoughts on how it could be improved, shoot me an email at the address below.
Shameless plug: I graduate from CS undergrad in a few weeks (4.0 BTW) and I'm spending far more time building stuff like this than applying for jobs, so if anyone is impressed by this and would be interested in hiring me that would be amazing. Check out my portfolio (all fullstack stuff but I’d love working in backend or lower-level stuff) or email me at jackson.a.furr@gmail.com.

Instructions

Enter source code into input box. Each instruction must be on a new line, and the code must contain at least a “main:” section
Click the “Compile & Load” button to compile the program and load it into memory
Click on “Execute Instruction” to execute each instruction individually, or click on “Run All” to run the entire program at once. Status and errors are currently shown in the dev console
Refresh before writing/starting a new program, or to stop a runaway program

Example Program

vars:
video int 5120
inst_len int 16

main:
add #3840 $video
mov $video %z
mov #128 %x
mov %inst %y
mov8 #2 [%z]
mov8 #3 [%z+128]
mov8 #4 [%z-128]
add #1 %z
sub #1 %x
cmp #0 %x
jlt %y

Registers (32-bit)

General Purpose:

Dedicated:

stack: points to end of used stack memory
base: points to start of current stack frame
heap: points to end of used heap memory
inst: points to the next instruction in the CODE segment

Flags

lt: true if src was smaller than dest
gt: true if src was smaller than dest
zf: true if result of mathematical operation was zero

Operands

Type	Specifier	Desc	type	formats	e.g.
Address	`@`	address of location	src, dest	uint16	`@1200`
Register	`%`	value in register	src, dest	text	`%stack`
Variable	`$`	value of variable	src, dest	text	`$age`
Pointer	`*`	address of variable	src	text	`*age`
Immediate	`#`	number	src	uint32	`#100`

Operations

Name	Form	Desc
Add	`add` src dest	add src to dest, set zf flag accordingly
Sub	`sub` src dest	subtract dest from src, set zf flag accordingly
Move	`mov` src dest	dest becomes source (32 bit)
Move8	`mov8` src dest	dest becomes source (8 bit)
Move16	`mov16` src dest	dest becomes source (16 bit)
Push	`pus` src	increment %stack, store src at new address
Pop	`pop` dest	store value at %stack address in dest, decrement %stack
Jump	`jmp` src	jump (set inst pointer) to src address
Jump Equal	`jeq` src	jump (set inst pointer) to src address if lt & gt flags are false
Jump Less	`jlt` src	jump (set inst pointer) to src address if lt flag is true
Jump Greater	`jgt` src	jump (set inst pointer) to src address if gt flag is true
Compare	`cmp` src dest	compare value in src to value in dest, set lt & gt flags accordingly

Indirect Access

Uses the value at the adress equal to the value in operand

Type	Format
Address	`[@20]`
Register	`[%x]`
Register+offset	`[%x+20]`
Variable	`[$age]`

Source Code Segments

Name	Required	Purpose
vars	No	Define global variables
main	Yes	Main function source code

Graphics

Video memory starts at 5120 and is 8k of memory, one for every pixel in the 128x64 screen. Write a byte to an address to change the corresponding pixel’s color.

These are the color values available currently:

Color	Value
white	0
black	1
red	2
green	3
blue	4

Example:

vars:
video int 5120

main:
mov $video %z
mov8 #4 [%z]
mov8 #2 [%z+1000]
mov8 #3 [%z+2000]
mov8 #1 [%z+5000]

Machine Instructions: 16 Bytes

Byte 1: Opcode
Byte 2: Access Type (Direct/Indirect)
Byte 3: Size
Byte 4: Src Type (Address/Value)
Bytes 5-6: Src Offset
Bytes 7-10: Src Value
Bytes 11-12: Dest Offset
Bytes 13-16: Dest Address